feat: add entry metadata system with compile-time typed values

Add `Metadata<B>` trait and `#[metadata(Entry)]` attribute macro
to attach arbitrary, compile-time-typed metadata to entries.
Implement `ProgramCollect::get_metadata<T>()` for runtime retrieval,
backed by a global registry populated by `register_metadata!`.

Extend `pathf` with `MetadataPattern` to resolve metadata types
across modules at build time. Add two examples demonstrating
metadata usage with and without pathf integration.

1 files changed, 3 insertions, 0 deletions

diff --git a/examples/example-combine-pathf-metadata/build.rs b/examples/example-combine-pathf-metadata/build.rs
new file mode 100644
index 0000000..d909431
--- /dev/null
+++ b/examples/example-combine-pathf-metadata/build.rs
@@ -0,0 +1,3 @@
+fn main() {
+    mingling::build::analyze_and_build_type_mapping().unwrap();
+}